DE102017216819B4 - Exhaust gas cooler and exhaust gas recirculation system with one exhaust gas cooler - Google Patents

Abstract

Exhaust gas cooler (10) with at least one exhaust pipe (12) for exhaust gas to be cooled, the at least one exhaust pipe (12) being surrounded by a housing (26) and / or a flange (22), characterized in that at the inlet (14) of the at least one exhaust pipe (12) in the direction of extent of at least one wall perpendicular to the direction of flow of the exhaust gas, the at least one exhaust pipe (12) is not attached to the housing (26) and / or the flange (22), the inlet (14) being of the at least one exhaust pipe (12) and at least one space (16) to the side between the wall (20) of the exhaust pipe (12) and the laterally adjacent housing (26) and / or flange (22) is provided, with a fastening point (28 ) of the at least one exhaust pipe (12) on the housing (26) through the gap (16) is shifted downstream in the flow direction of the exhaust gas, and the gap (16) extends in the flow direction of the exhaust gas from the inlet (14) to the fastening point ( 28) rec kt.

Description

TECHNICAL AREA

The invention relates to an exhaust gas cooler and an exhaust gas recirculation system with at least one such exhaust gas cooler.

In the field of internal combustion engines, it is common practice to recycle exhaust gas to some extent on the fresh air side in order to reduce fuel consumption and reduce emissions. The recirculated exhaust gas has to be cooled at least in certain operating states.

STATE OF THE ART

In this regard, it is, for example, from the JP 5 941 878 B2 known to guide the exhaust gas through numerous exhaust pipes that are accommodated in a housing, so that a flow with, for example, liquid coolant, in particular water / glycol, can be generated between the housing and the exhaust pipes, or between the exhaust pipes. In this case, however, the cooler heats up, in particular on the gas inlet side, which means that it has a significantly higher temperature here than in the further course. This leads to an inhomogeneous temperature distribution in the material of the cooler and thus to stresses. In particular, temperature changes of the gas as well as of the coolant, which occur due to the transient operating behavior of the internal combustion engine (e.g. cold start, load change, EGR rate, etc.) lead to further inhomogeneities in the temperature distribution with different material thicknesses and thus different temperature change rates, which lead to the stresses described to lead.

Inhomogeneities of this kind occur in a particularly critical form in the area of the gas inlet, since on the one hand the front thin edges of the exhaust pipes meet the uncooled hot exhaust gas mass flow and, due to the thin walls, the heat introduced can only be released slowly to the cooling water. Secondly, the exhaust pipes are usually laterally connected to a housing that has a significantly greater wall thickness and the temperature of which therefore changes with greater inertia, or the housing walls are not directly exposed to the hot exhaust gas mass flow. In some applications there is a thick-walled flange outside the housing, which further exacerbates the situation. The heated exhaust pipes in the inlet area expand, since the temperature of the housing and / or the flange has not yet changed sufficiently to result in a similar expansion, this different expansion leads to stresses.

The stresses lead to plastic deformation in the thinner component, the front edges of the exhaust pipe, which are compressed and / or ripple. When cooling, either the comparatively thin sheet cools down faster, or all of the components mentioned cool down at the same time, but the compressed sheet has to find its way back to its original position and stretch, this creates tensile stresses in the front edge of the exhaust pipe. This alternating load and plastic deformation leads to the failure of the material of the exhaust pipe. In this regard, it must also be taken into account that an exhaust gas cooler has to withstand the alternating load described several 100,000 times over its service life.

DE 10 2011 014 704 A1 relates to an exhaust gas device with an exhaust gas recirculation cooler. The exhaust gas recirculation cooler has a wall that forms a gas inlet base. Furthermore, the exhaust gas recirculation cooler has an inflow area which is fluidically decoupled from an area arranged on the inlet side of a heat exchanger. During operation, this area is filled with exhaust gas.

DISCLOSURE OF THE INVENTION

Against this background, the invention is based on the object of creating a permanently stable and at the same time inexpensive exhaust gas cooler.

This problem is solved by the exhaust gas cooler described in claim 1.

Accordingly, at least one space is provided at the inlet of at least one exhaust pipe to laterally adjacent components (a housing and / or a flange). In other words, at least one exhaust pipe is not attached to the surrounding components, ie the housing and / or the flange, in its direction of extent perpendicular to the flow direction, but directly adjacent to at least one wall of the pipe and on at least one side, preferably adjacent to all walls , there is a gap so that the pipe can expand freely perpendicular to the direction of flow when heated. Thus, the stresses and plastic deformations described above that lead to damage do not arise during expansion. The connection between the exhaust pipes and the housing takes place downstream of the gas, at a position where a homogeneous temperature distribution can be expected. In addition, the routing of the coolant can advantageously be designed in such a way that it cools such a connection well across all components.

It should be added that the wall of the exhaust gas pipe being considered can be viewed as a thin plate that extends on the one hand in the flow direction and on the other hand perpendicular to the flow direction. In addition, the thickness direction of the plate also extends perpendicular to the direction of flow, according to the invention, however, it is not important to provide gaps in the thickness direction, in other words with a horizontal orientation of the wall above and / or below the wall, but to the side, in other words " next to “the wall in the direction of extent described perpendicular to the direction of flow. If, unlike in the prior art, an interspace is provided here on at least one, preferably both sides, the effect according to the invention can be used.

It should also be added that the exhaust gas cooler according to the invention preferably has flat tubes, which can preferably be stacked in such a way that the long sides of the rectangular cross section of such a flat tube simultaneously form the delimitation of the exhaust gas tubes resting thereon. The spaces according to the invention are preferably provided for these long sides.

Preferred developments are described in the claims.

For the dimensions of the space described in the flow direction of the exhaust gas, good results are expected with a minimum length of 5 mm and / or a maximum extension of 2 cm.

The same applies to a dimension perpendicular to the direction of flow of at least 1 mm and / or up to 5 mm.

For extensive heat transfer from the exhaust gas to the coolant flowing around the exhaust pipes, it is preferred that at least one exhaust pipe has ribs or fins in its interior, which can preferably be designed to be corrugated in the direction of flow.

The advantages according to the invention can be used in particular in the case of an exhaust gas cooler with at least one exhaust pipe which has at least one wall with a thickness of 0.3 mm to 0.5 mm. Such a pipe is made comparatively thin and therefore “light”, and the measures according to the invention can at the same time avoid damage to the inlet.

The exhaust pipes are surrounded by a housing and / or a flange, which preferably have at least one wall with a thickness of 1.0 mm to 1.5 mm and / or a thickness of 5 mm to 8 mm. The housing and / or the flange are thus significantly thicker and more stable than the exhaust pipes and thus provide the exhaust gas cooler with an overall advantageous stability. At the same time, due to the measure according to the invention, they do not fix the inlet areas of the exhaust pipes, so that the problems described can be avoided.

Preferably, along the course of at least one exhaust pipe, further spaces are provided laterally next to the pipe in the flow direction, so that coolant can flow around here and, at the same time, a defined fastening of the exhaust pipes, for example on the surrounding housing, is achieved at defined points between the spaces described can be.

The exhaust gas cooler according to the invention develops particular advantages when it is used as an exhaust gas recirculation cooler.

Accordingly, the subject matter of the application is also an exhaust gas recirculation system with at least one such cooler.

Figure list

• 1 eine perspektivische Teilansicht eines erfindungsgemäßen Abgaskühlers; und
• 2 eine Schnittansicht des Einlassbereichs eines erfindungsgemäßen Abgaskühlers.

A preferred exemplary embodiment of the invention shown in the figures is explained in more detail below. Show it:

• 1 a perspective partial view of an exhaust gas cooler according to the invention; and
• 2 a sectional view of the inlet area of an exhaust gas cooler according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

As in 1 can be seen, has an exhaust gas cooler according to the invention 10 in the case shown a substantially rectangular cross-section and an elongated extension (in 1 to the top left). By means of a flange 22nd the exhaust gas cooler can be connected to an exhaust gas (return) line, which is not shown, or can be connected to a valve housing, in particular an EGR valve, (or to an EGR module). The flange can, for example, be cast, and the walls of the exhaust pipes described below, the ribs provided therein and the housing can be formed from appropriately bent sheet metal material. There are numerous exhaust pipes inside the exhaust gas cooler 12th which are essentially formed by plates aligned parallel to one another 20th made of metal, side, comparatively flat walls and ribs or fins arranged in between 18th that are better cut in the top view of 2 are recognizable. The plates 20th thus form walls of the exhaust pipes designed as flat pipes, which are comparatively thin and can therefore be subject to damage as a result of the expansion and contraction, as described above.

Out 2 shows that between the flange 22nd and the exhaust pipe 12th a housing 26th it is provided that the numerous exhaust pipes 12th surrounds, so that the laterally closed exhaust pipes can be flowed around with a liquid coolant, for example water, in order to cool the exhaust gas flowing through the exhaust pipes.

The case 26th is on the outside with the massive flange 22nd connected, but according to the invention is located at the inlet 14th of the respective exhaust pipe and to the side of this, in 2 to see left and right, a space in between 16 , which advantageously allows the exhaust pipe to expand when heated as a result of the flow of the hot exhaust gas. The lateral extension, in other words perpendicular to the direction of flow (in 2 from bottom to top) is in 2 to be seen left and right. The extension of the spaces 16 in the direction of flow up to a fastening point 28 the exhaust pipe on the housing 26th runs in 2 likewise from bottom to top and is preferably 5 mm to 2 cm. In the further course of the connection between the housing 26th and the exhaust pipe 12th are further spaces 24 intended.

In 2 the waveform of the ribs running in the direction of flow can also be seen in the embodiment shown.

The attachment point 28 in the exemplary embodiment shown extends at least some, for example 5 millimeters and / or up to 2 cm, in the direction of flow. Accordingly, the following can be seen. When the attachment point 28 in such an embodiment directly at the upstream end of the wall 20th , and thus would be provided at the inlet, it is due to the extension of the attachment point 28 It is not possible to supply coolant here in the direction of flow. Accordingly, the above-described problem arises caused by the gap according to the invention 16 showing the attachment point 28 to a certain extent shifts downstream in the direction of flow, is released.

In the embodiment shown, the flange 22nd a thickness measured in the direction of flow that is greater than the extent of the intermediate space 16 in order to achieve a stable execution overall.

According to the exemplary embodiment, the exhaust gas cooler has two inlets arranged next to one another and adjoining “stacked” groups of exhaust pipes, but the exhaust gas cooler according to the invention can also have a single inlet and an adjoining group of exhaust pipes, as well as more than two inlets and correspondingly provided exhaust pipes exhibit.

Claims (9)

Exhaust gas cooler (10) with at least one exhaust pipe (12) for exhaust gas to be cooled, the at least one exhaust pipe (12) being surrounded by a housing (26) and / or a flange (22), characterized in that at the inlet (14) of the at least one exhaust pipe (12) in the extension direction of at least one wall perpendicular to the flow direction of the exhaust gas, the at least one exhaust pipe (12) is not attached to the housing (26) and / or the flange (22), the inlet (14) of the at least one exhaust pipe (12) and at least one space (16) to the side between the wall (20) of the exhaust pipe (12) and the laterally adjacent housing (26) and / or flange (22) is provided, with a fastening point (28 ) of the at least one exhaust pipe (12) on the housing (26) through the gap (16) is shifted downstream in the flow direction of the exhaust gas, and the gap (16) extends in the flow direction of the exhaust gas from the inlet (14) to the fastening point ( 28) strete ckt. Exhaust gas cooler after Claim 1 , characterized in that at least one gap (16) extends at least 5 mm and / or at most 2 cm in the flow direction of the exhaust gas. Exhaust gas cooler after Claim 1 or 2 , characterized in that at least one intermediate space (16) extends at least 1 mm and / or at most 5 mm in a direction perpendicular to the flow direction of the exhaust gas. Exhaust gas cooler according to one of the preceding claims, characterized in that at least one exhaust pipe (12) has ribs (18) in its interior. Exhaust gas cooler according to one of the preceding claims, characterized in that at least one exhaust pipe (12) has at least one wall (20) with a thickness of 0.3 to 0.5 mm. Exhaust gas cooler according to one of the preceding claims, characterized in that the housing (26) has at least one wall with a wall thickness of 1 to 1.5 mm and / or at least one flange (22) has a thickness of 5 to 8 mm. Exhaust gas cooler according to one of the preceding claims, characterized in that at further points along the course of at least one exhaust pipe (12) in the flow direction intermediate spaces (24) are provided laterally next to the exhaust pipe (12). Exhaust gas cooler according to one of the preceding claims, characterized in that the exhaust gas cooler (10) is an exhaust gas recirculation cooler. Exhaust gas recirculation system with at least one exhaust gas cooler Claim 8 .

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